Hydrostatically driven machines having hydraulically actuated implements are known. Such machines typically use an internal combustion engine or another type of prime mover to provide power to one or more hydraulic pumps or transmission systems. Such machines typically operate under varied conditions requiring either power to propel the vehicle, power to operate the implements, or a combination thereof. For example, a loader operating to load loose material onto a truck may perform quickly repeating loading operations that require relatively low loading of the implement and propel systems. Alternatively, an excavator digging into virgin earth may encounter various obstacles, such as rocks and other debris, which demand momentary increased loading of the implement system until the obstacle breaks loose. It is often challenging for a machine to effectively address varying operating conditions while consistently maintaining high productivity, cycle time, and fuel economy.
Various features have been incorporated into electronic controllers associated with such machines to ensure proper operation. For example, an excavator machine attempting to lift a large or otherwise unmovable object encounters a spike in the load required by the implement. Because the implement is hydraulically driven, the increased load translates to an increased hydraulic fluid pressure at the hydraulic pump operating the implement. Hydraulic pumps are typically connected to the engine of the machine, such that an increased pressure at the pump under these conditions tends to stall the pump, and with it, the engine. To avoid such conditions, most modern machines have electronic controllers that limit the speed the engine may obtain during operation. This limit is implemented as a set-point that is either pre-programmed into the controller or as a series of discrete values that are selected by the machine operator based on the type of operation the machine is performing. This limit is known as an underspeed setpoint. Thus, when encountering a potential stall condition, the electronic controller operates to maintain engine speed at the selected setpoint.
Prior attempts to provide the operator with control over an appropriate engine or transmission underspeed set point, depending on the operating mode of the machine, have been provided. Past solutions generally include selector switches or knobs placed in the operator cab to allow an operator to select a desired setpoint operating mode for the machine. However, these predetermined and manually selectable modes of operation are not efficient in optimizing operation of the machine when the machine is operating under a mode that is not closely related to one of the modes the operator can select. Moreover, an operator may neglect to change the mode of the machine when performing mixed tasks. These limitations often result in under-optimized machine performance, increased fuel consumption and increased noise output by the machine, as well as higher cycle times when performing various tasks. From a broader perspective, under-optimized machine performance on a regular basis may lead to shorter service intervals and increased downtime for repairs and service.